A variety of comminuting apparatus are known for use with horizontal trim presses for subdividing scrap material that is generated by a trim press on a thermoforming line. More particularly, horizontal trim presses are configured to generate a scrap thermoformed web from which articles have been severed via the trim press. The web is delivered in a downward direction from the trim press and into a comminuting apparatus. Several such apparatus are sold as Chesaw® comminuting apparatus, Model Nos. Standard Series, C-Series, M-Series, and CLS, sold by Irwin Research & Development, of Yakima, Wash. Such a comminuting apparatus has an entrance duct formed by a pair of guide plates that guide scrap web into the comminuting apparatus from a trim press. However, there are gaps between the exit of the trim press and the entrance duct of the comminuting apparatus sufficient for an operator to insert a limb. Therefore, it is necessary to provide a protective cage about the area between the entrance duct of the comminuting apparatus and the exit of the trim press when incorporated into a thermoforming line. It is possible to construct a trim press with a custom-sized entrance duct that perfectly matches the exit clearance beneath a particular trim press. However, comminuting apparatus are frequently removed from beneath a particular trim press in order to clean out material from the comminuting apparatus when changing the materials that are being formed by a particular thermoforming line. Oftentimes, the comminuting apparatus may be subsequently placed beneath another trim press on another thermoforming line. It is usually the case that different trim presses on different thermoforming lines have different vertical clearances, which means that comminuting apparatus with a custom-sized vertical entrance duct clearance height will not interchangeably fit between different trim presses without leaving a potentially hazardous gap between the trim press exit and the comminuting apparatus entrance duct. Accordingly, a need exists to efficiently and easily adjust the vertical clearance height for an entrance duct of a comminuting apparatus when mating the comminuting apparatus beneath each one of several trim presses.